Tesla has improved the battery design of its robotaxi, the Cybercab, focusing on repairs, maintenance and cutting production costs. It also appears to have considered a potential future shift to lower-cost lithium iron phosphate (LFP) batteries while addressing the limited repairability of the structural battery used in models such as the Model Y.

InsideEVs, an electric vehicle outlet, said on Oct. 27 local time that the Cybercab packages its 4680 battery cells into four separate modules rather than binding them into a single integrated structure. That means if a problem occurs, the company can separate and repair or replace only the defective module instead of swapping the entire pack.

Robert Sumpf (로버트 섬프), Tesla's head of battery module and pack mechanical design, appeared on the YouTube channel "Munro Live" and said he would give the Model Y's structural battery a "D grade" himself. He said it was a great product for customers, but hard to build and had issues from a service perspective.

Structural batteries can improve space utilisation and cost efficiency by integrating cells as part of the vehicle body structure. But they also have a drawback in that partial repairs are difficult because the cells are fixed with rigid filler material. Munro & Associates previously assessed repairability as effectively "zero" after dismantling a Model Y fitted with a structural battery.

The Cybercab adopted a "semi-structural" design that makes module replacement easier to address those problems. Sumpf said fully integrating the battery into the vehicle structure could increase space for cells by about 10 percent and cut some costs, but the cost incurred during maintenance should be considered.

Another feature is that it has secured extra space inside the battery. The Cybercab currently uses nickel-manganese-cobalt (NMC) 4680 battery cells, but Tesla left room inside the pack in consideration of a potential future use of LFP batteries. Sumpf said it was designed to cope even if a lower energy-density battery chemistry is used, and that it also kept in mind the need to adopt LFP as production scales up.

LFP batteries generally have lower energy density than NMC, which could shorten driving range in the same space. But they have advantages in lower cost, thermal stability and charge-discharge durability, which could make them suitable for high-mileage robotaxis. Using the extra space in the Cybercab could also allow more cells to be installed, partly offsetting limits from energy density. Still, whether Tesla will actually switch to LFP and when it would apply it have not been decided.

This design also ties into how the Cybercab will be operated. Tesla engineers said the Cybercab is designed with a target lifespan of 500,000 miles, or about 800,000 km. For robotaxis that repeatedly operate for long hours, not only driving range but also repair time and replacement costs in the event of failures, as well as vehicle utilisation, determine business feasibility. Eric Arly, the Cybercab's chief engineer, also emphasised remanufacturing and repairability, saying that from the perspective of total cost of ownership, replacing the entire battery pack before reaching 500,000 miles would be costly.

Ultimately, the Cybercab's battery design appears to place more weight on lowering long-term operating costs than maximising energy density. If Tesla later introduces LFP batteries, there is room to cut both production costs and maintenance costs at the same time. Still, whether the current NMC batteries will actually be replaced with LFP will need to be confirmed as mass production expands.